Could multi-material 3D printing be the next step for AM?

Multi-material 3D printing is an innovative additive manufacturing technique that can be used to create objects with different materials and properties. By adding more complexity to a part, multi-material 3D printing can significantly improve the performance and functionality of parts. The technology thus opens up completely new possibilities for design and production - enabling the creation of objects that would otherwise be impossible. Currently, multi-material 3D printing is possible with a range of plastics, polymers and even silicones, making it an ideal solution for producing realistic, full-color prototypes and concept models. In this tutorial, we will learn about the benefits of multi-material 3D printing, the current processes available and the most common use cases and applications.

What are the advantages of multi-material 3D printing?

One of the main advantages of multi-material 3D printing is that complex parts with different material properties can be created in a single printing process. This differs from individual parts that need to be assembled to create a part with different material properties. Multi-material 3D printing can therefore reduce the number of steps required to produce an object, resulting in a faster product development cycle. Designers and manufacturers can also benefit from multi-material 3D printing, as the combination of different material properties (such as translucency and stiffness) within one part can take design validation and functional testing to a new level. Another benefit of using different materials in 3D printing is the ability to create color gradations. By mixing materials in different ratios, different color combinations and shades can be achieved without subsequent painting - saving time in post-processing.  

How does multi-material 3D printing work?

With multi-material 3D printing, different materials can be used in a single 3D printed object. While multi-material 3D printing is currently able to process materials such as thermoplastics and polymers, the combination of different metals or ceramics is not yet possible at this stage. Today, companies such as Stratasys and 3D Systems offer multi-material 3D printing solutions for prototyping and modeling. For example, the Connex multi-material system from Stratasys offers the following printing options:

Mixed installation space:

This option allows you to produce multiple parts from different materials - and therefore different properties - simultaneously in a single build. The Mixed Build Space option may be an ideal option for companies that require high volume prototyping.

Mixing part:

Multi-material 3D printers can also print parts with different properties in certain areas. print. Combining materials within a part eliminates the need to assemble separate parts.

Digital materials:

By mixing two or more materials, digital materials are used to create an object with enhanced properties and appearance that cannot be achieved when a part is 3D printed in a single material.

Which technologies are used for multi-material 3D printing?

Currently, material jetting is the most commonly used technology for multi-material 3D printing. During material jetting, print heads deposit droplets of a photosensitive material (or a mixture of materials or different materials by different print heads) that cure under ultraviolet (UV) light. The part is then created layer by layer using this process. Stratasys and 3D Systems are the leading manufacturers of multi-material 3D printers based on material jetting technology. For example, the Connex™ 3D printing system from Stratasys works with two or three different plastic materials during the 3D printing process. This results in the finished part having different properties (such as stiffness and flexibility) at the same time.  

Which materials can be used for multi-material 3D printing?

Currently, the most widely used material options for 3D multi-material printing are acrylic-based photopolymer resins and composites of rigid plastics and elastomers. For example, last year 3D Systems introduced a new large format multi-material ProJet MJP 5600 3D printer that works with a range of resins and their combinations to create fully assembled prototypes and complex geometries with multiple material properties. Although materials can vary in mechanical properties, advances in 3D printing materials mean that engineered composites are also available. One of the latest innovations in multi-material 3D printing is silicone 3D printing, a technology developed by ACEO®, a subsidiary of Wacker Chemie AG. ACEO®'s innovative silicone technology enables the production of silicone parts with different colors, hardnesses and properties. One useful application of this is the creation of silicones that have insulating and conductive properties, as these can be used to create an assembled part with integrated electrical conductivity.

Applications of multi-material 3D printing

The possibilities of multi-material 3D printing are endless, with a wide range of use cases in the consumer, medical and other industries. Currently, multi-material 3D printing is mainly used in product development. For example, swimming equipment company, Speedo, has used the technology to produce items such as goggles and other swimming equipment as part of the product development cycle. Other products, such as functional prototypes of seals, tires and shoe soles, are also possible with 3D multi-material printing. With this technology, the design and function of the product can be tested and verified before it goes into production. Because multi-material 3D printing can combine translucent and opaque materials, the medical industry has adopted the technology to create realistic anatomical models for educational purposes as well as patient-specific models for pre-operative planning and training. The technology also enables the creation of translucent parts with internal colored structures that can be used to visualize fluid flows or test medical devices. Mechanical engineers in the automotive, aerospace and other industries can use multi-material 3D printing to create functional prototypes with the appearance of the final product (colors, labels, etc.). In addition, multi-material 3D printing enables the production of molds for short injection molding and tooling runs without the need for assembly. An interesting element of advanced multi-material 3D printing is the ability to create parts with integrated functions, which is particularly useful for electronic devices. Nano Dimension Ltd. has recently made a breakthrough in the development of multi-material 3D printing inks. Conductive and dielectric inks can now be used simultaneously to produce electrically functional parts, circuits and antennas.  

Challenges

While multi-material 3D printing is currently mainly used for prototyping, it still offers enormous potential for the production of parts made from different materials and a combination of mechanical properties. Research is therefore ongoing into how to overcome the existing challenges for multi-material 3D printing of functional parts. The difficulty lies in developing a scalable and repeatable production process that can deliver high-quality end pieces made from multiple materials. This is particularly challenging for metals and ceramics, as there are significant physical limitations when melting two materials together that have different melting temperatures and other material properties, for example. However, Belgium-based Aerosint claims to have developed a unique multi-material powder bed process to produce end pieces with metals in sight. The technology, which works with polymers, controls the distribution of two different types of powders at the voxel level, which are then sintered together.

Future prospects

Another fascinating area of research is multi-material bioprinting, which could have a revolutionary impact on areas such as tissue engineering, regenerative medicine and biosensing. Today, however, multi-material 3D printing offers tremendous opportunities for product development and validation testing, as the technology enables the creation of realistic 3D printed models and prototypes with different properties. Ultimately, the next step for multi-material 3D printing will be to make the transition to the production of final parts with different properties.tion to the production of end parts with integrated functions and improved mechanical properties. This area of development, which is already seeing a lot of research activity, will expand the potential of additive manufacturing to new horizons.